1. Field of the Invention
This invention relates to rotary piston devices and more particularly to a casing inner diameter contacting seal assembly for such devices.
2. Prior Art
Rotary piston machines, such as rotary engines, pumps, compressors and the like which utilize a piston having an outer diameter configuration which contacts the inner diameter of an enveloping casing at at least one region of the casing are known to the art. It has been common to provide one or more laminar working members in operative engagement with the piston and providing a slidable seal on the inner diameter surface of the casing. Such working members, or sealing members, generally engage plane surfaces on the piston such as, for example, planar slot walls extending into the piston from the periphery thereof which are contacted by planar surfaces on sides of the working member (seal member). In some examples, it has been known to replace the laminar working members or seals with cylindrical seal members which have only a line contact with the planar surface in the piston.
In some prior art machines, it has been known to guide the lower ends of the working members by sliding them on an internal cam surface, the outline of which corresponds to that of the casing inner diameter surface.
Although the use of cylindrical or roller-like working members does avoid producing a tilting moment of the sealing member, with the resultant danger of premature wear which is common with straight or laminar working members having plane surfaces, the line contact parallel with the axis of rotation of the piston is not advantageous for transmitting working pressures from the seal member to the piston and vice versa. In addition, the effectiveness of the seal between the chambers formed by division of the internal space between the casing inner diameter and the piston outer diameter divided by the seal is not adequate.
It would therefore be an advance in the art of rotary piston machines to provide a more effective seal assembly between the inner diameter of the casing and the outer diameter of the piston which avoids the heretofore encountered tilting moment problems of laminar seals while avoiding the less effective sealing problem which arise from prior cylindrical or roller-like seal members.